This program project grant supports a number of studies related to environmental carcinogenesis. These studies are: 1. Epidemiology of gastrointestinal cancers - U.S. and Yugoslavia (E.L. Wynder). 2. Metabolic activation of 5-methylchrysene (D. Hoffmann, S.S. Hecht). 3. Metabolic epidemiology of large bowel cancer (B.S. Reddy). 4. Metabolic epidemiology in breast cancer (P.B. Hill). 5. The role of nutritional deficiency and alcohol in the etiology of head and neck cancer (G.D. McCoy). 6. Cell analysis of neoplastic development in the rat liver (G.M. Williams). 7. Epidemiologic studies of shipyard welders (J.M. Stellman).